Sharp 75" LCD TV repair - Videokarma.org TV - Video

maxhifi · #1 02-03-2020, 10:32 AM

May have an opportunity to bring home a Sharp 75" TV, I would estimate it is 5 years old. Problem as follows:

Off state: Blue power LED is slowly flashing
Turn on with remote: Blue power LED comes on solid, LCD screen comes on, and displays SHARP logo. Screen flashes, and then set goes dead completely, does not respond to remote control. A short while later, the blue power LED starts flashing slowly again, and the set will respond to another cycle.

Based on above, does it sound like this set can be salvaged? I am assuming it is a power supply issue, which is encouraging, but I've never worked on an LCD TV before.

SpaceAge · #2 02-03-2020, 01:57 PM

I would lean towards that being fixable. I have a similar power cycling issue with a 32” LG I bought from a former roommate who moved away. After messing around with it I found wiggling the power cord where it plugs into the back of the TV resolves the issue temporarily. So somethings wrong with the power supply, possibly something as simple as a bad solder joint or loose connection. I’ll get to it one of these day. How much would the TV cost you?

maxhifi · #3 02-03-2020, 03:10 PM

It should be free, I just wonder if it is worth my time or not.

SpaceAge · #4 02-03-2020, 03:29 PM

Only you can decide that. If it’s 4k I wouldn’t hesitate but I’m guessing it’s 1080p. It may be a Quattron with the RBGY pattern... a gimmick for sure, but I personally like oddball stuff like that.

JohnCT · #5 02-03-2020, 04:15 PM

Quote:

Originally Posted by maxhifi

May have an opportunity to bring home a Sharp 75" TV, I would estimate it is 5 years old. Problem as follows:

Off state: Blue power LED is slowly flashing
Turn on with remote: Blue power LED comes on solid, LCD screen comes on, and displays SHARP logo. Screen flashes, and then set goes dead completely, does not respond to remote control. A short while later, the blue power LED starts flashing slowly again, and the set will respond to another cycle.

Based on above, does it sound like this set can be salvaged? I am assuming it is a power supply issue, which is encouraging, but I've never worked on an LCD TV before.

Model number?

We see an inordinate amount of LED issues with most TVs 5 years and newer, and the newer they are, the more LED problems they have.

I use an LED tester that can "ring" the strings and provide a running voltage for 20ma worth of input (LEDs are powered by a regulated current, the voltage reading depends on the number of LEDs used and the condition of them).

If the TV has two or more strings of LEDs, we can measure the differences between the strings, assuming of course that each string is driving the same number of LEDs, and not all TVs do.

So, if you have a string of LEDs out, the controller IC will detect an undercurrent and either shut down that one string (unusual) or the whole array (more common). Also, a single shorted LED or a single weak LED that is dropping more than it's 3V or 6V rating can trip the LED circuit to shutdown if it's configured to be hair trigger.

John

maxhifi · #6 02-03-2020, 04:24 PM

It's still mounted in an inaccessible location, so I can't get the model number yet.

I am thinking it is most likely not 4k, but hard to be sure. If there is a bad LED, what is the resolution? Is it possible to swap in a new strip, or is that impractical for some reason?

Titan1a · #7 02-03-2020, 04:35 PM

I believe this is repairable but TAKE YOUR TIME! You can create more damage that would be non-repairable. The LED strip is cheap and easily procurable should it need replacement.

maxhifi · #8 02-03-2020, 05:08 PM

Quote:

Originally Posted by Titan1a

I believe this is repairable but TAKE YOUR TIME! You can create more damage that would be non-repairable. The LED strip is cheap and easily procurable should it need replacement.

Cheap and easily procurable... awesome, I will pick it up. Would be interesting to see inside a flat panel set.

JohnCT · #9 02-03-2020, 07:15 PM

Quote:

Originally Posted by maxhifi

If there is a bad LED, what is the resolution? Is it possible to swap in a new strip, or is that impractical for some reason?

It's doable, but there is a learning curve. Most professionals have either cracked a display or damaged one of the bonded ribbons or address board(s) on many an early repair. Out of the several thousand flats I've done, I've lost about 15 or so.

You have nothing to lose really, but if you disassemble the display, set up your work area so the TV is about a foot away from the wall or some other barrier.

As you remove the mask, the retaining pieces, the 3 to 5 polarizer sheets, then finally the display, you can stand them up against the wall in order. Reassembling is simply lowering everything back down in the same order (and more importantly) in the same orientation. If you get a polarizer sheet upside down or backwards, it will affect the picture.

It's a good idea to pick up several small suction cup grabbers (harbor freight) to support the display as you lift it up and out of the light box. The display is a lamination of two plastic sheets surrounding a thin glass layer where the LCDs live. This glass is so thin it couldn't support it's own weight without the plastic shell, but even with the plastic, it can still flex and crack if you try to lift it with a finger nail. So several suction grabbers and a friend will lift the display out of the frame with as little stress as is possible.

John